This invention relates to ceramic mirrors for use in laser and X-ray apparatuses, cameras, and other precision optical instruments and the like.
Mirrors for use with precision optical instruments and the like are predominantly made of glass, ruby, sapphire and the like, and also of single crystal ceramics. In recent years alumina and SiC have partly come in use as polycrystalline ceramics.
Glass-based mirrors are made relatively thick to make up for the inadequate strength and fragility, and therefore the heavy weight and large size of the mirrors as a whole have been a problem. Polycrystalline alumina, SiC, and other ceramic materials are used in the form of sintered bodies after grinding and lapping. None of them have proved fully satisfactory in respect of the properties such as surface smoothness and optical properties, because the pores inherent to the ceramic materials remain exposed on the lapped surfaces.